Forest products industry effluents contain dissolved or mechanically separated wood components. The major wood components are lignin, hemicelluloses and cellulose. The pulping processes preferably separate lignin and hemicelluloses. The dissolved lignin and hemicelluloses are burned for process energy and chemical recovery in the most pulping processes. Some of the fibers and dissolved wood components escape the process to the effluent treatment plant. The recovery, separation, and upgrade of the degraded hemicelluloses into chemicals and derivatives are currently not practiced. These hemicelluloses are most commonly consumed during activated sludge wastewater treatment. The activated sludge is then land filled or burned.
Specifically, the steam cooking process dissolves predominantly hemicelluloses in temperatures above 160 degrees C. The solution containing hemicelluloses removed from this process is termed extract. The extraction of hemicelluloses using steam cooking and blowing through pressure reducing valve, commonly termed “blow valve”, is used in the production of medium and hard density board. Because of the low concentration of hemicelluloses in the extract, when the hemicelluloses are hydrolyzed to sugars, the subsequent concentration of sugars through evaporation before fermentation to produce ethanol is energy intensive.
Research indicates that ethanol, acetic acid and their byproducts can be derived from the extract. Especially, predominantly hardwood, containing bark, produces extract rich in acetic acid and sugars as taught by Amidon et al. in (U.S. Patent Application No. 2007/0079944 A1, Apr. 12, 2007).
The present inventors have now developed a process wherein the hemicelluloses in the extract can be converted to chemical products in an energy efficient process.